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  • 1
    Electronic Resource
    Electronic Resource
    Growth process conditions of vertically aligned carbon nanotubes using plasma enhanced chemical vapor deposition (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 5308-5317 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of vertically aligned carbon nanotubes using a direct current plasma enhanced chemical vapor deposition system is reported. The growth properties are studied as a function of the Ni catalyst layer thickness, bias voltage, deposition temperature, C2H2:NH3 ratio, and pressure. It was found that the diameter, growth rate, and areal density of the nanotubes are controlled by the initial thickness of the catalyst layer. The alignment of the nanotubes depends on the electric field. Our results indicate that the growth occurs by diffusion of carbon through the Ni catalyst particle, which rides on the top of the growing tube. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1410322
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  • 2
    Electronic Resource
    Electronic Resource
    Nanotechnology Synthesis of carbon 'onions' in water (2001)
    [s.l.] : Nature Publishing Group
    Nature 414 (2001), S. 506-507 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The fabrication of carbon nanomaterials usually calls for expensive vacuum systems to generate plasmas and yields are disappointingly low. Here we describe a simple method for producing high-quality spherical carbon nano-'onions' in large quantities without the use of vacuum equipment. The ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35107141
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  • 3
    Electronic Resource
    Electronic Resource
    Stationary carbon cathodic arc: Plasma and film characterization (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2237-2244 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma characteristics of a new arc mode on carbon referred to as the "stationary cathodic arc'' are reported. Particularly, optical emission spectroscopy, probe and ion energy distribution measurements are used to compare the properties of the stationary arc with the normal "random cathodic arc'' on carbon. The measurements revealed that the plasma properties of both arc modes are similar. In addition, we have correlated the plasma characteristics to the film properties. Carbon films deposited using the stationary arc were found to have a surface particle density equivalent to those deposited using the filtered cathodic vacuum arc. The macro-particle free films were found to be highly tetrahedral and compressively stressed. Both the sp3 fraction and stress values were strongly dependent on the ion energy with maximum values of 85% and 9.4 GPa, respectively, occurring at ≈50 eV. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362656
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  • 4
    Electronic Resource
    Electronic Resource
    Ion energy and plasma characterization in a silicon filtered cathodic vacuum arc (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 1287-1291 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The plasma generated by a silicon filtered cathodic vacuum arc has been investigated using a Faraday cup and Langmuir probes. Ion energy distributions for arc currents ranging from 30 to 80 A were measured. Mean ion energies were found to range from 8 to 18 eV. The ion saturation current density varied from 0.1 to 1 mA/cm2 depending on both the arc and filter coil currents. The energy distributions were fitted by a sum of Gaussians spaced according to the gas dynamic model for ion acceleration at the cathode spot. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362654
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of the heterojunction on the field emission from tetrahedral amorphous carbon on Si (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1908-1910 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to study the influence of the back barrier on the electron emission properties of tetrahedral amorphous carbon (ta-C), we have deposited identical films on p and n+ Si. The valence and conduction band offsets were measured for ta-C on p and n+ Si using in situ x-ray photoelectron spectroscopy and optical spectroscopy. From the band measurements it is shown that there is a substantial back barrier to emission. We show that for films having very similar properties, the electron emission can be influenced by the ta-C/Si heterojunction. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1310623
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  • 6
    Electronic Resource
    Electronic Resource
    Evolution of sp2 bonding with deposition temperature in tetrahedral amorphous carbon studied by Raman spectroscopy (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 1419-1421 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two transitions in the bonding are found in tetrahedral amorphous carbon (ta-C) films as a function of deposition temperature. The total sp3 fraction shows a sharp decrease at a transition temperature of order 250 °C. In contrast, visible Raman finds that the sp2 sites show a gradual ordering into the graphitic clusters through the sharp bonding transition. The optical gap and resistivity show a similar, gradual transition. This indicates that the sp2 cluster size determines the optical gap, even when the sp2 content does not change. The Raman I(D)/I(G) peak ratio is found to vary inversely with the square of the gap. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126050
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  • 7
    Electronic Resource
    Electronic Resource
    Field emission from dense, sparse, and patterned arrays of carbon nanofibers (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2011-2013 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We compare the field emission characteristics of dense (109 nanofibers/cm2), sparse (107 nanofibers/cm2), and patterned arrays (106 nanofibers/cm2) of vertically aligned carbon nanofibers on silicon substrates. The carbon nanofibers were prepared using plasma-enhanced chemical vapor deposition of acetylene and ammonia gases in the presence of a nickel catalyst. We demonstrate how the density of carbon nanofibers can be varied by reducing the deposition yield through nickel interaction with a diffusion layer or by direct lithographic patterning of the nickel catalyst to precisely position each nanofiber. The patterned array of individual vertically aligned nanofibers had the most desirable field emission characteristics, highest apparent field enhancement factor, and emission site density. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1461868
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  • 8
    Electronic Resource
    Electronic Resource
    Field emission from short and stubby vertically aligned carbon nanotubes (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2079-2081 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electron emission from vertically aligned carbon nanotubes grown by plasma enhanced chemical vapor deposition has been measured using a parallel plate anode and a 1 μm tungsten probe. The field emission characteristics were measured as a function of the nanotube diameter, length, and areal density. It was found that less densely populated "short and stubby" nanotubes with diameters of 200 nm and heights of 0.7 μm showed the best emission characteristics with a threshold voltage of 2 V/μm and saturation emission current density of 10 mA/cm2. A triple junction between nanotube, substrate, and vacuum is proposed to explain our results.© 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1406557
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  • 9
    Electronic Resource
    Electronic Resource
    Uniform patterned growth of carbon nanotubes without surface carbon (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1534-1536 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In order to utilize the unique properties of carbon nanotubes in microelectronic devices, it is necessary to develop a technology which enables high yield, uniform, and preferential growth of perfectly aligned nanotubes. We demonstrate such a technology by using plasma-enhanced chemical-vapor deposition (PECVD) of carbon nanotubes. By patterning the nickel catalyst, we have deposited uniform arrays of nanotubes and single free-standing aligned nanotubes at precise locations. In the PECVD process, however, detrimental amorphous carbon (a-C) is also deposited over regions of the substrate surface where the catalyst is absent. Here, we show, using depth-resolved Auger electron spectroscopy, that by employing a suitable deposition (acetylene, C2H2) to etching (ammonia, NH3) gas ratio, it is possible to obtain nanotube growth without the presence of a-C on the substrate surface. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1400085
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of ion energy and substrate temperature on the optical and electronic properties of tetrahedral amorphous carbon (ta-C) films (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 139-145 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The properties of amorphous carbon (a-C) deposited using a filtered cathodic vacuum arc as a function of the ion energy and substrate temperature are reported. The sp3 fraction was found to strongly depend on the ion energy, giving a highly sp3 bonded a-C denoted as tetrahedral amorphous carbon (ta-C) at ion energies around 100 eV. The optical band gap was found to follow similar trends to other diamondlike carbon films, varying almost linearly with sp2 fraction. The dependence of the electronic properties are discussed in terms of models of the electronic structure of a-C. The structure of ta-C was also strongly dependent on the deposition temperature, changing sharply to sp2 above a transition temperature, T1, of (approximate)200 °C. Furthermore, T1 was found to decrease with increasing ion energy. Most film properties, such as compressive stress and plasmon energy, were correlated to the sp3 fraction. However, the optical and electrical properties were found to undergo a more gradual transition with the deposition temperature which we attribute to the medium range order of sp2 sites. We attribute the variation in film properties with the deposition temperature to diffusion of interstitials to the surface above T1 due to thermal activation, leading to the relaxation of density in context of a growth model. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364000
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